Many food products such as cheese, coffee, etc. are packaged in sealed plastic bags to retain the food's freshness. But conventional plastic packaging for food can be difficult to open. For example, many bags have top and bottom heat-pressed peelable seal zones, and to open the package the user must pull apart the sides of the bag to peel open the seal. That can be rather difficult and frustrating, particularly for elderly and very young persons who may not have strong fingers.
To remedy this problem, there has been developed an improved food package with a bubble formed in the top seal zone. The user compresses the bubble between his or her fingers and the pressure of the air on the seal zone causes the seal zone to fail. Bursting the bubble forcibly expels the air in the bubble outwardly through the top seal zone at the failure site and out of the top of the bag. Then the top free edges of the bag, which were separated from each other by the bursting bubble, can be gripped to pull the sides of the bag apart to open the bag. Thus, this pop-to-open bag is easier to open that conventional packaging.
However, this type of bag must be carefully and precisely made so that the bubble bursts reliably and properly to allow for the desired ease of opening. To date, this type of bag has only been known to be manufactured with the bubble formed by hand in the seal zone. This adds significantly to the cost and makes this type of bag too expensive for widespread use.
Accordingly, it can be seen that needs exist for improved machines and methods for manufacturing sealed plastic packages. In particular, there is a need for machines and methods for cost-effectively and reliably manufacturing pop-to-open packages that open easily and reliably. It is to the provision of solutions meeting these and other needs that the present invention is primarily directed.